Comparing the Size of the Human Genome With a Computer Operating System
\[3 \times 10^9\]
of these letters in a human genome.We can write the human genome in binary code using the following labelling:
A is labelled 00
G is labelled 01
C is labelled 10
T is labelled 11
With this labelling ACTTGC becomes 001011110110 for example.
When written in binary code like this, the genome is twice as long, containing about
\[6 \times 10^9\]
digits. 1 kilobit contains \[1024 \simeq 10^3\]
digits.1 megabit contains
\[1048576=10^6\]
digits.1 gigabyte contains
\[1073741824=10^9\]
digits.The human genome is then about 3 gigabits long. 1 byte equals 8 bits so the genome is about
\[\frac{3 \times 10^9}{8} \simeq 400 \]
megabytes long. As of 204 a typical home computer operating system is 700 megabytes long, about twice as long as the human genome. 
